The present invention relates to a plasma processing apparatus for processing an object to be processed (process object) by utilizing plasma.
As the degree of integration of semiconductor devices increases, enlargement of the diameter of a wafer representing a process object and fine structuring of circuit patterns have been accelerated. Under the circumstances, in processing a process object by utilizing plasma, for example, a parallel-planar plasma processing apparatus (prior art 1) using a radio frequency (RF) has been used. JP-A-9-27485 (prior art 2) discloses a plasma processing apparatus based on inductive coupling. JP-A-7-307200 discloses a plasma processing apparatus in which a plurality of antennas each having a length equaling xc2xc of wavelength of an admitted RF are arranged radially in a plasma generating chamber so as to generate plasma. A similar antenna structure is described in JP-A-9-293682, according to which a plurality of antennas are studded in a plurality of opposing electrodes are arranged in such a way that antennas studded in one electrode group and antennas studded in the other electrode group are parallel thereto and are staggered to provide a comb-shape structure (prior art 3). JP-A-10-134995 describes a parallel-planar UHF plasma apparatus in which a radio frequency in UHF band is supplied to a disk-shaped antenna by means of a coaxial cable, the diameter of the antenna being set to a predetermined value (prior art 4).
Prior art 1 lacks plasma distribution control means and when the kind of gas and the pressure are changed, distribution of radical compositions and that of reaction products change, making it sometimes difficult to make the processing distribution uniform.
Prior art 2 sometimes has difficulties in establishing compatibility between improvements in selectivity in etching and distribution controllability.
Prior art 3 has sometimes difficulties in making the plasma density uniform in the radial direction.
Prior art 4 has difficulties in adjusting the distribution when gas, pressure or power is changed.
Accordingly, an object of the present invention is to provide a plasma processing apparatus for realizing the generation of plasma suitable for processing in a wide parameter region in a method of generating plasma by using a radio frequency in VHF or UHF band and a magnetic field.
According to one aspect of the invention, a plasma processing apparatus comprises a vacuum vessel, a processing chamber arranged in the vacuum vessel and supplied with gas, a support electrode arranged in the processing chamber to support an object to be processed, radio frequency providing means for supplying a frequency in UHF or VHF band to the processing chamber, and magnetic field forming means for forming a magnetic field in the processing chamber, wherein the radio frequency providing means includes an antenna having a groove or a step (a difference in level) in its surface opposing the process object.
Preferably, the depth or width of the groove or step is thicker than a plasma sheath and is smaller than xc2xc of wavelength of the radio frequency. Preferably, the antenna has its surface made of Si or SiC. Preferably, the antenna has a conical recess or boss formed in the center of its surface adjoining plasma. Preferably, the antenna takes a form curved downward concavely or convexly at a constant curvature. Preferably, a planar member made of Si or SiC, or C and being physically or effectively thinner than a skin depth of the radio frequency is arranged on the surface of the antenna. Preferably, a disk-shaped antenna is formed with a slit opening, a planar member made of Si or SiC, or C is arranged on its surface adjoining plasma, the radio frequency is supplied to the processing chamber through the planar member.
In the plasma apparatus comprising the radio frequency providing means for supplying the radio frequency in UHF or VHF band to the disk-shaped antenna and the magnetic field forming means, the recess or boss can be deemed as an uneven portion formed in the surface of disk-shaped antenna adjoining plasma. The uneven portion is sized to such an extent that the plasma can invade a space between the antenna surface and the uneven portion, in other words, the space is sufficiently larger than a plasma sheath, amounting up to at least about 1 mm or more and less than xc2xc of wavelength of the radio frequency. Further, the uneven portion is preferably sized to about 1 cm or more. Preferably, the antenna surface is made of Si or SiC.
Other objects, features and advantages of the present invention will be apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.